Will it be The Joy of Six (V6, that is) or The Annoy of Six? In all likelihood, the correct answer is: it all depends.
In July, IBM announced that it would deliver a new release of i5/OS, V6R1, sometime in 2008. When in 2008 is not yet clear.
The available list of new features and enhancements is somewhat vague and likely incomplete, but they fall mainly in the areas of encryption, virtualization, integrity, Java support, and Web deployment. An attempt to read the tea leaves left after drinking in the announcement suggests that Web deployment is receiving particular attention.
Should you upgrade to V6R1 when the time comes? You'll have to decide that after the benefits are more fully fleshed out. However, if you're using a particularly old System i machine, it's not even an option unless you also invest in new hardware. V6R1 won't run on older systems. The plan is to support System i POWER5 Models 515, 520, 525, 550, 570, 595 and POWER6 Model 570. Thus, a box with an "AS/400" label slapped on it probably won't run V6R1 (unless, of course, you slapped the tag on yourself over top the "System i" label to protest against IBM's system-naming flippancy). Second-generation, but not first-generation, systems with the "iSeries" label will support the new operating system.